Traditionally, most commercially available inkjet printers have a print engine which forms part of the overall structure and design of the printer. In this regard, the body of the printer unit is typically constructed to accommodate the printhead and associated media delivery mechanisms, and these features are integral with the printer unit.
This is especially the case with inkjet printers that employ a printhead that traverses back and forth across the media as the media is progressed through the printer unit in small iterations. In such cases the reciprocating printhead is typically mounted to the body of the printer unit such that it can traverse the width of the printer unit between a media input roller and a media output roller, with the media input and output rollers forming part of the structure of the printer unit. With such a printer unit it may be possible to remove the printhead for replacement, however the other parts of the print engine, such as the media transport rollers, control circuitry and maintenance stations, are typically fixed within the printer unit and replacement of these parts is not possible without replacement of the entire printer unit.
As well as being rather fixed in their design construction, printer units employing reciprocating type printheads are considerably slow, particularly when performing print jobs of full colour and/or photo quality. This is due to the fact that the printhead must continually traverse the stationary media to deposit the ink on the surface of the media and it may take a number of swathes of the printhead to deposit one line of the image.
Recently, it has been possible to provide a printhead that extends the entire width of the print media so that the printhead can remain stationary as the media is transported past the printhead. Such systems greatly increase the speed at which printing can occur as the printhead no longer needs to perform a number of swathes to deposit a line of an image, but rather the printhead can deposit the ink on the media as it moves past at high speeds. Such printheads have made it possible to perform full colour 1600 dpi printing at speeds in the vicinity of 60 pages per minute, speeds previously unattainable with conventional inkjet printers.
The ink ejection nozzles in modern inkjet printers are typically MST (micro systems technology) devices in the form of a printhead integrated circuit (IC). They are fabricated on silicon wafer substrates using lithographic etching and deposition techniques. Printhead IC's have closely packed nozzles which provide good image resolution image but introduces some production difficulties. One issue is providing the printhead IC with power and print data from the print engine controller. A flexible printed circuit board (flex PCB) is usually used for this. Flex PCB's have tracks of conductive material in a polymer film. The tracks are spaced so that they are in registration with a line of bond pads on the printhead IC. The tracks are then directly connected to the bond pads. This requires the flex PCB to be very accurate and a high degree of precision when aligning the flex PCB and the bond pads. Consequently, this can be a time consuming stage of the overall printhead production process.
The situation is exacerbated in the production of the pagewidth printheads discussed above. The printhead IC's that make up a pagewidth printhead are generally longer than the printhead IC's used in scanning type printheads. Hence the line of bonds pads on each IC is longer so the track spacing must match the bond pad spacing more closely. It will be appreciated that a slight inaccuracy in the track spacing can be accommodated by the width of the bond pad. However, the spacing inaccuracy compounds with each successive track across the flex PCB so by the end of a long line of bond pads, the slight inaccuracy is no longer accommodated by the pad width.
Accordingly, there is a need to provide a more time efficient and commercially practical method for connecting the tracks of a flex PCB with the corresponding bond pads of a printhead IC.